DISEASES OF THE HOG. 131 



PLETHORA. 



This is a morbid increase of blood beyond tlie 

 wants of the system. It is not, however, a mere 

 augmentation of volume in the circulating fluid 

 that is entitled to this name. This may result from 

 an excess of the watery ingredient and is not in- 

 compatible with the state of the animal which is 

 opposite to that of plethora. There must be a mor- 

 bid increase of those constituents of the blood upon 

 which its nutritive and stimulating properties de- 

 pend and to which it owes its peculiar character, 

 such as the red corpuscles, fibrin and albumen. 

 There may or may not be any increase of bulk. It 

 is not necessary that there should be an absolute 

 increase of the blood in order to the existence of 

 the disease. The quantity may remain precisely 

 the same and yet if the wants of the system for the 

 support of its various functions should diminish 

 the phenomena of plethora may result; for it is the 

 loss of balance between the supply and consump- 

 tion, the former being in excess, that constitutes 

 the affection. (Wood). 



Causes of Plethora: A loss of equilibrium be- 

 tween the supplying and expending processes is 

 the immediate cause of plethora. Digestion and 

 absorption are relatively more vigorous than nu- 

 trition and secretion. Thus feeding pigs more than 

 they ought to be fed will produce this effect, espe- 

 cially if the animal has little exercise. In some 

 cases digestion and absorption may be healthy 

 while nutritioi? and secretion may be in a deranged 



